To restore lost seagrass, just add some otters. According to a new study in Proceedings of the National Academy of Sciences, these adorable critters help counteract the harmful effects of fertilizer pollution.

Seagrass provides valuable marine habitat, sequesters carbon, and shields coastlines from storms. But nutrient run-off from farms can trigger overgrowth of algae, which then block sunlight from reaching the seagrass.

The researchers studied seagrass recovery in Elkhorn Slough, California, which has suffered from rising fertilizer pollution over the last several decades. In the early 1980s, only 2 hectares of eelgrass remained. But after sea otters arrived, the area of eelgrass growth expanded by six times.

The otters contributed to the recovery by eating crabs, the authors suggest. The number of sea slugs, which crabs prey on, increased. Those slugs then grazed on the algae, allowing the seagrass to flourish. — Roberta Kwok | 27 August 2013

Source: Hughes, B.B. et al. 2013. Recovery of a top predator mediates negative eutrophic effects on seagrass. Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1302805110.